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95 Cards in this Set
- Front
- Back
- 3rd side (hint)
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What is the cellular membrane? |
The boundary between the living cells and their surroundings |
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What type of permeability does the CM exhibit? |
Selective. Some substances pass more easily than others. |
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What controls the passage across CM? |
Transport proteins |
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What is the CM made of? |
Phospholipids |
They are the most abundant lipid in the PM |
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Phospholipids are amphipathic, true or false? |
True |
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What makes phospholipids amphipathic? |
They contain both hydrophobic and hydrophilic compounds. |
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What happens when the phospholipids create a bilayer? |
It can create a boundary between two aqueous components. |
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What makes up the dynamic structure of the PM |
Hydrophilic heads Hydrophobic tails Water molecules Transmembrane channel |
4 things |
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What kind of models are cellular membranes |
CM are fluid mosaics of lipids and proteins |
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What is the fluid mosaic model? |
The membrane is made up of many protein molecules bobbing in a fluid bilayer of phospholipids |
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What is the distribution of proteins in the membrane? |
Not random. |
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How are membranes held together? |
Membranes are held together mainly by weak hydrophobic interactions. |
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Are the lipids and proteins in the membrane static? Why or why not? |
No. Most of the lipids and some proteins can move sideways. Only rarely do they flip from one phospholipid layer to the other |
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How does temperature affect membrane fluidity? |
As temperature drops, fluidity of membrane decreases. |
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What happens when there is a reduction in the fluidity of the membrane? |
It affects the function of the membrane |
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What temperature does the membrane solidify? |
It depends upon the composition of the lipids. |
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How do fatty acids affect membrane fluidity? |
Membranes rich in fatty acids are more fluid than those in saturated fatty acids. |
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Why do unsaturated fats promote fluidity? |
Unsaturated fats have kinks in the tails that prevent packing, which causes them to stay liquid at lower temperatures. |
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What role does cholesterol have on the membrane fluidity at warm temperatures? |
At warm temperatures, the cholesterol restrains the movement of phospholipids. |
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What role does cholesterol have on membrane fluidity at cooler temperatures? |
At cool temperatures, it maintains fluidity by preventing tight packing. |
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Why might there be difference in lipid composition of cell membrane in different species? |
They might have adaptations to specific environmental conditions. Ability to change the lipid compositions in response to temperature changes evolved in organisms that live where temperatures vary. |
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What makes the fluid mosaic model a mosaic? |
Collection of multiple different proteins, embedded in the lipid bilayer. Phospholipids form the bulk of the membrane. |
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What determines most o the membrane’s function? |
Proteins! |
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What are the 2 major types of membrane proteins? |
Integral and peripheral Proteins |
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What are integral proteins? |
Enters into the hydrophobic region of the lipid bilayer. |
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What type of major protein are transmembrane proteins? |
Integral proteins |
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What makes up integral proteins? |
Hydrophobic core made of non polar amino acids, coiled into a helices. |
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What are peripheral proteins? |
They are bound to the surface of the membrane but NOT embedded |
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Peripheral proteins pass through the hydrophobic core of bilayer, true or false? |
False. Peripheral proteins do not pass through the core of the bilayer. |
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Where are peripheral protein located on the cytoplasmic side? |
They are attached to cytoskeletal components. |
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What six functions do cell surface membranes carry out? |
Transport Enzymatic activity Signal transduction Cell cell recognition Intercellular joining Attachment to the cytoskeleton and extra cellular matrix |
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How do cells recognize each other? |
By surface molecules on the extra cellular surface of the PM |
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What are carbohydrates bound to? |
Covalently bonded to lipids, forming glycolipids Covalently bonded to proteins, forming glycoproteins |
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What is the arrangement of proteins, lipids, or associated carbs in the PM? |
Asymmetrical distribution |
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What determines when the membrane is built? |
The ER and the Golgi Apparatus |
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Why is the PM selectively permeable? |
It regulates the cell’s molecular traffic and exchange of materials with surroundings. |
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What are the emergent properties of membranes? |
Properties of membrane vastly different and broader than properties of individual components |
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How easily do hydrophobic molecules pass through the lipid bilayer? |
Easily. They can dissolve and pass through the membrane rapidly |
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How easily do hydrophilic molecules (ions and polar molecules) pass through the bilayer? |
They do not cross the membrane easily. |
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What role do proteins play in the membrane? |
The proteins built into the membrane play roles in regulating transport. |
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What do transport proteins do? |
Allow passage of hydrophilic substances across the membrane |
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What is diffusion? |
Molecules spreading out evenly into the available space |
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How do molecules move in diffusion? |
Each molecule moves randomly, but overall population of molecules moves down the concentration gradient. |
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What is dynamic equilibrium? |
Equal number of molecules cross the membrane in each direction |
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Is work done to move substances down the concentration gradient? |
No work is done. No energy needed. |
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What is passive transport? |
The diffusion of a substance across a biological membrane is passive transport as no energy is expended by the cell. |
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What is osmosis? |
The diffusion of water across a selectively permeable membrane |
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How does water move across the membrane? |
Water diffuses across a membrane moving from a lower to a higher solute concentration. |
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What is water trying to do during osmosis? |
Water is trying to dilute a concentrated solute. |
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What determines the behaviour of a cell in solution? |
Solute concentration and membrane permeability |
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What is tonicity? |
The ability of a surrounding solution to cause a cell to gain or lose water. |
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What determines the tonicity of a solution? |
It depends on its concentration of solutes that cannot cross the membrane, relative to that inside the cell. |
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What is osmoregulation? |
The control of solute concentrations and water balance. |
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What is an isotonic solution? |
Solute concentration is the same as that inside a cell. There is no net water movement across the plasma membrane. |
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What is a hypertonic solution? |
Solute concentration is greater than that indie the cell, so the cell loses water Water wants to dilute the higher solute concentration outside of the cell |
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What is a hypotonic solution? |
Solute concentration is less than that inside the cell so the cell gains water. Water wants to dilute the higher solute concentration inside the cell. |
BOOM |
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What function does the cell wall play in relation to water. |
Cell walls help maintain water balance. |
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What happens to the water balance inside an isotonic cell. |
There is no net movement of water into the cell, so the cell became flaccid. |
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What happens to the water balance inside a hypertonic cell? |
In a hypertonic environment, plant cells lose water. The membrane pulls away from the cell wall, causing the plant to wilt, a potentially lethal effect called plasmolysis. |
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What is plasmolysis? |
The membrane pulls away from the cell wall, causing the plant to wilt, a potentially lethal effect called plasmolysis. |
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What happens to water balance in cells with cell walls in a hypotonic solution? |
A plant cell in a hypotonic solution swells until the wall opposes uptake. |
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What is turgor pressure? |
Happens in hypotonic solution. turgor pressure provides non woody plants mechanical support. |
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What is facilitated diffusion? Is energy required? How do molecules move? |
Transport proteins speed the passive movement of molecules across the plasma membrane. Energy is not required Molecules still move down their concentration gradient. |
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What do ion channels in channel proteins do? |
Ion channels facilitate the transport of ions. Some ion channels, called gated channels, open or close in response to a stimulus |
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Why do carrier proteins change shape? |
The change in shape can be triggered by the binding and release of the transported molecule. |
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Does Active Transport require energy? |
Yes. Usually in the rom of ATP hydrolysis, to move substances against their concentration gradients. |
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How is energy used in active transport? |
The terminal phosphate group from ATP is transferred directly to the transport protein |
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What is the purpose of active transport? |
Active transport allows cells to maintain concentration gradients that differ from their surroundings |
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What is the sodium potassium pump? |
A transport protein that is energized by transfer of a phosphate group from the hydrolysis of ATP |
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What is the first step of the sodium potassium pump? |
Cytoplasmic sodium binds to the SPP. |
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What is the second step of the SPP? |
Sodium binding stimulates the phosphorylation by ATP |
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What is the third step of the SPP? |
Phosphorylation leads to a change in protein shape, reducing its affinity for sodium which is released outside. |
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What is the fourth step in the SPP? |
The new shape has a high affinity for potassium which binds on the extra cellular side and triggers release of the phosphate group. |
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What is the fifth step in the SPP? |
Loss of the phosphate group restores the proteins original shape, which has a lower affinity for potassium. |
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What is the sixth step in SPP? |
Potassium is released affinity for sodium is high again and the cycle repeats. |
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What is the electrochemical gradient? |
The combined forces that drives diffusion of ions across a membrane. Chemical and electrical. |
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What is membrane potential? |
Voltage across membrane, due to differences in distribution of ions across a membrane. Cytoplasm side: negative Extra cellular side: positive |
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What is an electrogenic pump? |
A transport protein that generates voltage across a membrane SPP an Proton pump |
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What is cotransport? |
Occurs when active transport of a solute indirectly drives transport of other substances. Diffusion of the first substance down concentration is coupled to transport of second substance against own concentration gradient. |
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What is the electrochemical gradient? |
The combined forces that drives diffusion of ions across a membrane. Chemical and electrical. |
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Small molecules and water pass through the LB or via transport proteins, true or false? |
True |
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What is cotransport? |
Occurs when active transport of a solute indirectly drives transport of other substances. Diffusion of the first substance down concentration is coupled to transport of second substance against own concentration gradient. |
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Do large molecules (polysaccharides and proteins) cross the membrane? |
Yes, via bulk vesicles. |
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How does bulk transport occur? |
Via endocytosis or exocytosis and requires energy. |
Can also recycle and remodel plasma membrane |
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How does bulk transport occur? |
Via endocytosis or exocytosis and requires energy. |
Can also recycle and remodel plasma membrane |
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What is exocytosis? |
Transport vesicles migrate to the membrane, fuse with it, and release their contents outside the cell. |
Many secretory cells use exocytosis to export their products. |
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What is endocytosis? |
A Reversal of exocytosis involving different proteins. The cell takes in macromolecules by forming vesicles from the plasma membrane. |
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What are the three types of endocytosis? |
Phagocytosis Pinocytosis Receptor mediated endocytosis |
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What is phagocytosis? |
A cell engulfs a particle in a vacuole. The vacuole fuses with a lysosome to digest the particle. |
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What is phagocytosis? |
A cell engulfs a particle in a vacuole. The vacuole fuses with a lysosome to digest the particle. |
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What is pinocytosis? |
Molecules dissolved in droplets are taken up when extra cellular fluid is gulped into tiny vesicles. “Cellular drinking” |
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How does bulk transport occur? |
Via endocytosis or exocytosis and requires energy. |
Can also recycle and remodel plasma membrane |
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What is phagocytosis? |
A cell engulfs a particle in a vacuole. The vacuole fuses with a lysosome to digest the particle. |
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What is pinocytosis? |
Molecules dissolved in droplets are taken up when extra cellular fluid is gulped into tiny vesicles. “Cellular drinking” |
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What is receptor mediated endocytosis? |
Binding of specific solutes to receptors triggers vesicle formation. Receptor proteins, receptors, and other molecules from the extra cellular fluid are transported in the vesicles. Emptied receptors are recycled to the plasma membrane. |
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